A Korean team of astronomers has investigated the rotational properties of galactic neighbors and discovered something peculiar: Galaxies that are near each other all seem to rotate in the same direction.
The role of galaxy interactions is crucial to understand how they evolve. While very close neighbors might dramatically disrupt each other, galaxies further afield might only tug on each other a bit and collide after billions of years. After a certain distance though, the interactions become much more subtle – or so we thought.
Two papers have recently been written on this topic. In a first published earlier this year in The Astrophysical Journal, the researchers saw this coherent rotation in relatively close groups of galaxies up to 2.6 million light-years away. These galaxies are close enough to strongly influence each other gravitationally, which appears to be happening from their formation.
A second paper, published last month in The Astrophysical Journal, extended the rotational investigation to almost 50 million light-years. The researchers looked at 445 galaxies within 400 million light-years from Earth. They found that even when galaxies are tens of millions of light-years apart, they continue to rotate in the same direction. The synchronicity is still present.
“This discovery is quite new and unexpected. I have never seen any previous report of observations or any prediction from numerical simulations, exactly related to this phenomenon,” lead author Joon Hyeop Lee, from the Korea Astronomy and Space Science Institute Daejeon, South Korea, told Vice.
While direct interaction can explain the close-by coherence, the synchronicity from tens of millions of light-years cannot be explained in the same way. In the paper, the team suggests that the alignments are effects produced by the internal motions of large-scale structures of the universe. Essentially, previously unseen interactions and motions affect galaxies across the universe.
Galaxies and clusters of galaxies are all embedded in a structure called the cosmic web. What we know about the cosmic web comes from simulations and observations of how galaxies are distributed, but its more subtle characteristics elude us. A filament of this mysterious structure was only recently observed.
If there are internal motions within this web of material, we are yet to find out. As our instruments might not be up to the task for a while, the researchers suggest investigating the perplexing phenomenon using simulations.